Realization of the population inversion in a conjugated polymer by a single or double stimulating pulse

By applying a single or double stimulating pulse to a conjugated polymer, we theoretically realize the population inversion between the generated intragap states. The simulations are performed within the framework of an extended version of the one-dimensional Su-Schrieffer-Heeger tight-binding model combined with a nonadiabatic evolution method. In discussions, we mainly compare the stimulating intensity thresholds between the two different pumped modes, at which the population inversion in polymer is reached. It is found that, the stimulating intensity threshold can be remarkably reduced by employing a double pulse rather than a single one. Effect of the lasting time for each pulse on the threshold is also discussed. We then propose a new optical-pumped mode to realize the population inversion in polymers, which is potentially of great importance for polymer lasers.